Effect of a lysine-enriched diet on L-lysine transport by the brush-border membrane of the chicken jejunum.
The influx of L-lysine into apical vesicles from the chicken jejunum occurs through two systems, one with low Michaelis constant (K(m)) and features of system b0,+ and the other with relatively high K(m) for L-lysine and with properties of system y+. In the present study the effect of a lysine-enriched diet (Lys, containing 68 g L-lysine/kg dietary protein, control animals 48 g/kg) on L-lysine uptake through both transport systems was investigated. Results show that 1) lysine enrichment had no effect on either body weight or the efficiency of food utilization. 2) In Lys-fed animals, the mediated L-lysine influx was best fitted to the two-system model with y+ and b0,+ activity. 3) In the presence of an Na+ gradient, total L-lysine uptake is significantly higher in Lys-fed animals than in control birds (about 40% increase). 4) Lys diet increases K(m)b0,+ 6-fold (KSCN gradient) and 12-fold (NaSCN gradient) and maximum velocity (Vmax) by 6- and 20-fold, respectively. The effects of Lys enrichment on the y(+)-like system are only observed on the Vmax and in the presence of a Na+ gradient (30% increase). 5) Na+ is involved in the activation of the transport process in the Lys-fed chickens, but there is no correlation between external Na+ concentration and L-lysine influx. In conclusion, both b(0,+)- and y(+)-like transport systems are upregulated by dietary lysine but with different kinetic profiles; the high-capacity y(+)-like carrier shows a Vmax increase without changes in K(m), whereas the low-capacity b(0,+)-like system shows an increase in Vmax as well as in the K(m).
Torras-Llort
M
M
Unitat de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona, Spain.
Soriano-García
J F
JF
Ferrer
R
R
Moretó
M
M
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001835:Body Weight; D002645:Chickens; D004032:Diet; D004734:Energy Metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D007413:Intestinal Mucosa / Q000502:physiology*; D007583:Jejunum / Q000502:physiology*; D007700:Kinetics; D008239:Lysine / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013393:Sucrase / Q000378:metabolism; D013861:Thiocyanates / Q000494:pharmacology
D013861:Thiocyanates; C024553:sodium thiocyanate; D013393:Sucrase; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose; D008239:Lysine; D005033:Ethylmaleimide; C009941:potassium thiocyanate